reduce sexual harassment from males. Growth The offspring juvenile stage lasts between 18 days and eight weeks. Once again, changes in temperature affects these numbers; colder temperatures decrease and higher temperatures can increase maturity. This species can have several generations within their breeding period because of their fast rate of growth. The usual lifespan is between one and two years, as determined by stress factors in their habitats. Sexual selection in this species is based on the size of the male. Females tend to choose larger, more aggressive males. Females tend to choose areas of shallow water with dark soil cover for brooding sites, while juveniles prefer more rooted plants in which to hide. The main human-induced change that affects the growth rate and life history of G. holbrooki is the water temperature. Ecology Invasive species Eastern mosquitofish have become an invasive species in Australia. Eastern mosquitofish were introduced into New South Wales in the 1920s to control mosquitoes, but provided no further benefit over small Australian native fish. Further, they cause harm to native fauna that have an aquatic larval stage. Mosquitofish are aggressive, fin-nipping harassers of other fish, and pose a serious threat to native Australian fish and aquatic invertebrates. Negative impacts on rainbowfish species and at least one frog species have been documented. Several rainbowfish populations appear to have become extinct due to the impacts of introduced Gambusia. Compounding the issue, Eastern mosquitofish have the ability to thrive in many different environmental conditions which are usually lethal to other fish species. Australia set up conservation management plans to try to save native species from G. holbrooki. One such management plan included releasing a chemical known to kill mosquito larvae. The chemicals used were found to have a strong effect on the G. holbrooki, but they became tolerant to most of them fairly rapidly unless amounts considered unsafe for native species were used. Another strategy tried, and failed, to decrease this invasive species was electrocuting a lake known to have been invaded. The cost and loss of native fish was so great, this method was dropped. The main reason it failed was mosquitofish stay in the shallows, which receive the smallest charge from the electrification method used. Later tests also revealed this species has a high tolerance for electrical shock, but the exact mechanism that allows this still seems to be questionable. Predators Little research has been done